Commercial high and low pressure steam systems and traps

patdolan

high pressure steam supplying numerous cooking kettles. Positive pneumatic control shut off valves on steam supply and steam return to condensate. Each kettle has an individual steam trap on line prior to entering common condensate return. All kettle steam traps and the entire condensate drain line discharge pipe (about 60') is full with water to the condensate pump which needless to say runs non-stop. I can find no reason why there are individual steam traps on the system. Since all discharge lines are full and the rate of discharge is matched to the discharge rate of the condensate pump they do not function as designed.
I am considering, during a drainage re-pipe eliminating all individual traps and have one located at the inlet of the condensate pump just in case some kettles are dropped from service and the condensate line clears of water.

I respect Dead Men Theory but in this case I am pre-disposed to think one trap will suffice as all kettles have the positive valves on supply and discharge so ......... comments that are real are welcomed.
Pat

jumper

What kind of steam trap? Some traps control jacket's steam temperature. The control valves presumably act on kettle's interior temperature? I'd stick with individual traps on each kettle.

patdolan

I considered that. As a precautionary action I can leave them and probably will. I see nothing that indicates two levels of temperature, jacket and interior as you mentioned. Thanks for replying. I appreciate it.

aircooled81

The load in each indavidual kettle may vary when in use. Plus, whats to stop the steam from path of least resitance when each kettle requires? I wonder if indavidual traps was a safe guard to verrying condensate loads.
Plus, 1 big trap may not function as well or last as long as many small traps?
Have you thought about the cause of excess condensate? If assuming the condensate pump was sized accordingly, is there a chance you arent carrying dry steam to these kettles? Or lost a lot of insulation to them?
If one trap is leaking past, could this attribute to excess condensate?
Just thinking out loud here.

deadmansghost

You mentioned that the condensate receiver tank pump runs non stop. I am wondering if you have a tank venting problem or the tank float switch has a problem.

Pumpguy

Lets look at the sizing and selection of the condensate pump.

Do you know what the condensing capacity is of each kettle? Multiply this by 2, or better yet 3, and then by the number of kettles. This will tell you the size of condensate receiver you should have. Then size the pump. Ideally the pump should empty out the tank, or at least cycle between the settings of the float switch, in one minute. In addition to the volume capacity, the pump(s) discharge pressure needs to overcome the piping friction, elevation head, and any pressure at the destination.

A duplex condensate pump set with a mechanical alternating, or two non-alternating lead / lag float switches, will run together under peak load conditions and provide twice the pump-out volume capacity.

Another thing to consider about condensate pumps is NPSH and temperature. If the condensate is much over 190 degrees F., you may need to go to special 2'NPSH pumps to handle the hot water. These have both a conventional centrifugal impeller, and ahead of that is an axial flow prop. These are offered by several manufacturers, Shipco, Federal, and ITT Hoffman Domestic IIRC.

jumper

Pumpguy said:

Another thing to consider about condensate pumps is NPSH and temperature. If the condensate is much over 190 degrees F., you may need to go to special 2'NPSH pumps to handle the hot water. These have both a conventional centrifugal impeller, and ahead of that is an axial flow prop. These are offered by several manufacturers, Shipco, Federal, and ITT Hoffman Domestic IIRC.

If you need low NPSH transfer there's other technologies. Regenerative,big inlet,and jet. All about equally inefficient.

patdolan

Thank you to the individuals who commented above.

Steam use does vary when kettles are in and out of use however with mechanical valves on both steam supply and condensate return I don't foresee that being as much of a problem as you would expect in a normal steam application. I also believe the condensate steam return is full because of an incorrectly sized pump. I think it was sized so it did not overflow not necessarily to work correctly.

Thanks for thinking of tank venting and float switch issues. I already considered those possibilities.

Each kettle develops 45 gallons of condensate per hour so I am sizing the drain lines, receiver and pump GPM accordingly. I will use the 2 x"s volume formula to account for the cycling use of various kettles. The piping discharge head formulas for the return to the boiler room will dictate that part of the installation. Likely I will split the condensate returns into two separate pumps as the discharge rates can be kept under 1,500 gallons an hour that way.

One other consideration I have to deal with is this is an enormous food processing plant. I have to factor into some steam back pressure (failed steam traps) in the common condensate return lines just prior to the receiving tank in the main boiler plant. Nothing like a simple calculation!

I am familiar with the duplex condensate pumps with mechanical alternating float switches and because of the volume I will require that type installation.

Thanks very much for the following which I copied below - old age creates memory lapses and I completely forgot about temperature.
"Another thing to consider about condensate pumps is NPSH and temperature. If the condensate is much over 190 degrees F., you may need to go to special 2'NPSH pumps to handle the hot water. These have both a conventional centrifugal impeller, and ahead of that is an axial flow prop. .."

Thanks to all very much.
Pat

Pumpguy

Being in a food processing plant, you might want to consider stainless steel construction. Not all manufacturers offer stainless steel pump housings. I can offer more suggestions off line if you're interested.

Sailah

We manufacture a lot of OEM steam traps for jacketed kettles by Market Forge, Blodgett, Vulcan etc. if the trap is one of ours I can probably make some recommendations based on the condensate loads just need to know the model. Many of the lower pressure traps just don't cope well with high pressure and have a short lifespan. We've developed a higher pressure trap that works well up to 300PSIG and fits in the same form factor.

I guess I can't see a reason why a single larger trap wouldn't work as you have control valves, provided that the trap is sized appropriately for the pressure and condensate load. I'd also echo comments made above about the trap being able to modulate the temp and load for various kettles.

Sounds like you have a condensate problem first and then need to ensure the traps are working second.

patdolan

Thanks. I am doing all 304 stainless and have located 2" traps in stainless as well that will work at a 65 psi pressure. I have enough information and knowledge to go through the door with. Now it's up to the customer. I have thankfully also found some good resources as well.
Pat